As network availability in devices spreads, and network access coverage increases, there is an increasing demand to create a network of connected things or devices. Where the first drive of the telecommunications industry was to connect locations to each other, and ask users to travel to one of the connected locations, and the second drive of the industry was creating mobile connections so that people could be connected regardless of locations, a third phase of connectivity is being entered. In this third phase, there is an interconnection of devices.
Whether these devices are mobile, such as actuators in transportation systems, or fixed in locations such as sensors on a utility meter, devices are being connected to each other and to network applications or services.
However, a problem is foreseen in that as the number of devices will increase, the problem of managing these devices will also grow. Furthermore, the manner in which the devices are connected to a network can affect how they are managed and communicate.
As among one of the recognized authorities on standardization of communication technology, the European Telecommunications Standards Institute (ETSI), has taken the initiative to develop standards to support industry for enabling ease of connectivity between the devices i.e. sensors and actuators, as well as applications and services.
By means of standards, innovation across industry is facilitated, enabling exposure of data and information as well of provision of services.
ETSI has defined a standard for machine-to-machine (ETSI M2M) communication where devices communicate and exchange information via a defined structure of database-like resources. The standard is described in a.o. the following documents:
TS 102 689—Service Requirements: which provide a high level requirements for an M2M Service Layer
TS 102 690—Functional Architecture. The architecture which entities are required as to deploy device communication and management in an M2M network.
TS 102 921—mIa, dIa and mId interfaces. The document provides the protocol specification for the three reference points mIa, dIa and mId.
The ETSI M2M suite, comprising the standards listed above, provides a Machine-to-Machine (M2M) architecture with a generic set of capabilities for M2M services and provides a framework for developing services independently of the underlying network.
The ETSI M2M suite is generally based on a number of defined physical entities and a number of defined resources. The resources comprise information to be shared or exchanged, and are organised in so called Service Capability Layers (SCLs), according to a REpresentational State Transfer (RESTful) architecture style.
The RESTful architecture style, generally applied by ETSI M2M, represents a tree wherein the SCL maintains a resource structure where the information to be shared or exchanged is stored and updated.
Communication to and from the resources, comprised by the SCLs, is defined by procedures over dedicated interfaces, called “reference points”.
The entities forming a network are organised in a pyramid like structure where (multiple) devices (sensors and actuators) form the basis and a Network node, network domain server, comprising a Network Service Capability Layer (NSCL) forms the top of the pyramid.
The device might be a very simple device, such as a contact switch sensor, only able to provide on-off data, or an actuator such as a relay to turn on or off a heating element. On the other extreme a device can be a complex remote sensor with a local application that provides compressed and encrypted strings of data on e.g. received radiation units on request.
ETSI M2M has defined the concepts of an M2M application and an M2M Service Capability Layer (SCL), being processing units comprised by physical entities. The application has to register over a defined reference point with an SCL. The SCL to be registered with, called “the local SCL” in ETSI M2M terms, is either the SCL locally available in the same entity where the application resides, or if not locally available, in the first higher SCL in the pyramid.
The SCL enables an application to use the M2M communication suite. The ETSI M2M SCL can generally be seen as a database, having a defined record structure, using defined interfaces, the reference points, for communication with other SCLs and Applications, and is arranged to perform functions such as relaying information to other SCLs, store and forward functionality, expiration time handling, policy enforcement, etc.
ETSI M2M had defined (until now) a number of different entities, a Device (D and D′ also known as “D prime”), a Gateway (G) and a Network node (N). The D′ entity comprises an Application only. The D, G and N entities comprise an SCL an may further comprise an Application.
The G entity has been introduced to connect D′ entities in a local area level. The G entity enables M2M communication to other entities in the M2M network by means of its SCL.
Multiple G entities comprising Gateway SCLs (GSCLs) and optionally Gateway Applications (GAs) could be connected to an N entity such that a pyramid-like structure is formed.
In this way a Network Application (NA) comprised by the N entity can communicate with- or control- the connected D- and G- entites.
ETSI M2M indicates that an address of a resource representing Device Application (e.g. with identifier DA1) registered with the SCL of an NSCL (e.g. with identifier NSCL1) has the identifier:
“<sclBase for NSCL1>/applications/DA1”.
The pyramid-like topological structure of the entity which hosts DA1 is not represented in this identifier. The sequence is independent from underlaying physical networks.
Device applications are generally understood as applications that in case of a sensor, retrieve the data of the sensor and store (or “update” in M2M terms) the data into the resource of the one or more SCLs where the application has been registered to. In case of an actuator, the application may e.g. read the resource of the SCL where the application has been registered with, or reacts on a notification message, and controls the actuator according to the value indicated in the resource read or notification received respectively.
Gateway- and Network applications are understood as applications that process data received from Device Applications and submit requests to Device Applications to be executed.
There is a substantial demand to connect numerous devices which may connect via fixed and cellular data networks as well as wireless network interface such as WiFi (IEEE 802.11).
However not all devices can be expected to reside in a single network, operated by a single M2M provider, just as in the ETSI M2M standards listed above is presented.
A problem is raised in how devices can initialise and establish communication when different M2M networks are maintained by different M2M service providers, having no D entities connected via the same G or N entities.
As an example of the problem stated, a solution is required for a situation where an entity in a first M2M Service provider network has to retrieve information that is stored in a resource residing in one or more entities of a second M2M Service Provider network.